A laminated glass including two glass plates integrated through an interlayer film for a laminated glass containing a thermoplastic resin such as plasticized polyvinyl butyral is widely used for automotive windshields.
Such automotive windshields are produced, for example, by a vacuum deaeration method.
In the vacuum deaeration method, an interlayer film for a laminated glass is sandwiched between at least two glass plates to give a laminate. The laminate is placed in a rubber bag and vacuum suctioned for removal of air remaining between the glass plates and the interlayer film so as to be preliminarily pressure bonded. Then, the laminate is pressurized with heat, for example, in an autoclave for final pressure bonding to provide an automotive windshield.
In the process for producing a laminated glass by the vacuum deaeration method, deaeration properties upon stacking a glass plate and an interlayer film for a laminated glass on top of each other are important. The interlayer film for a laminated glass therefore commonly has minute projections and recesses formed on at least one surface for the purpose of ensuring the deaeration properties in production of a laminated glass. In particular, when recesses, among the projections and recesses, each have a groove shape with a continuous bottom (shape of an engraved line) and such recesses in the shape of engraved lines are regularly formed side by side in parallel with one another, excellent deaeration properties can be exhibited (see, Patent Literature 1).
An exemplary method for producing a laminated glass is a nip roll method. In the nip roll method, a laminate including at least two glass plates and an interlayer film for a laminated glass interposed between the glass plates is carried on a conveyor through a heating zone to be heated to a certain temperature, and then passed between nip rolls to be pressure bonded under heating, while the glass plates and the interlayer film are squeezed for reduction of air remaining therebetween. The glass and the interlayer film for a laminated glass were thus closely bonded.
When an interlayer film for a laminated glass conventionally used in production of a laminated glass by the vacuum deaeration method is used in production of a laminated glass by the nip roll method, deaeration of the resulting laminated glass may be insufficient.